Grain Refinement in As-Cast 7475 Al Alloy under Hot Multiaxial Deformation

Effect of pass strain (*D*e) on grain refinement was studied in multiaxial compression (MAC) of a coarse-grained 7475 Al alloy at 763K under a strain rate of 3x10-4 s-1. The value of *D*e influences significantly the kinetics of grain refinement. MAC of *D*e=0.7 results in a substantial grain refinement in high strain, finally leading to formation of a fine grain structure with a mean size of 7.5 *mm and the volume fraction of about 85%. In contrast, MAC of *D*e=0.4 leads to formation of a smaller volume fraction of fine grains with the similar grain size. The grain refinement mechanisms operating under hot MAC are discussed in some details.